Unlike its sister hemovascular system, the lymphatic circulation largely escapes preclinical and clinical investigation owing to the limited methods available to non- invasively image lymphatic architecture and function. The lack of in vivo lymphatic imaging severely limits our ability to understand lymphatic biology in preclinical models, to evaluate lymphatic components of human disease of increasing prevalence, and to stratify hereditary lymphatic diseases for efficient genotyping. Moreover, there is sparse understanding of the physiological responses of lymphatic function in both health and disease. In this application, we seek to develop functional 2-D lymph imaging as well as 3-D lymph angiography using near-infrared (NIR) time independent and dependent techniques and associated imaging agents. We seek to evaluate lymphatic architecture and physiologic responses in health and disease and more importantly, to develop an important and missing imaging tool for lymphatic research. Specifically, our aims are to: (1) Demonstrate human imaging of lymphatic function and its physiological response in normal subjects and patients who suffer from lymph dysfunction using 2-D planar NIR imaging techniques;(2) Develop 3-D optical tomography or angiography methods for evaluating lymph architecture and function in major lymphatic trunks using novel imaging agents;and (3) Demonstrate the use of new NIR lymphatic imaging agents for 3-D optical lymph angiography in humans. If successful, we will be able to demonstrate functional and architectural imaging in symptomatic and familial asymptomatic Milroy's and lymphedema distichiasis patients who are molecularly diagnosed through genotyping. The ability to image lymphatic function will enable us to understand the role of the lymphatics in health and disease. PUBLIC HEALTH RELEVANCE: Malfunctioning lymphatics and lymphatic function are implicated in many diseases of increasing prevalence. Yet Milroy's and Lymphedema distichiasis are rare, congenital forms of lymphedema which provide a window to understand lymph dysfunction. In this work, we develop an approach to image for the first time, dynamic lymph function and architecture in these patients using novel near-infrared contrast agents employed in microdose administration for optical imaging.